1. Field of the Invention
This invention relates generally to elevator control systems and especially to elevator monitoring apparatus.
In particular, the device of this invention concerns an improved tape guide for use with an elevator hoistway tape.
2. Background Information
Elevator control systems, among other functions, monitor the speed and location of an elevator cab assembly within an elevator hoistway by sensing movement of the cab relative to a stationary tape vertically suspended in the hoistway. The tape is commonly provided with indicia such as a series of apertures, or magnetic elements, or light-reflective vanes. A sensor unit mounted on the elevator cab detects the indicia and generates corresponding output signals that are transmitted to an elevator controller.
Tape guides mounted on the elevator cab assembly engage opposite edges of the tape to precisely position the tape with respect to the sensor unit. The tape guides include guide slots for slidingly receiving the respective edges of the tape. The relative displacement of the tape within the guide slots, over a period of time, result in wear changes in the guide slot which effect sensing performance. This can be detected during routine maintenance of the elevator system and corrected by replacement of the tape guides. However, the elevator servicing requires temporarily disabling the elevator cab for the removal and replacement of the tape guides. This can be a time-consuming and costly procedure and an inconvenience to passengers.
Several attempts have been made to extend the useful life of tape guides including a tape guide construction having reciprocal tape slots on opposite faces of the guide. The life of the tape guide can be prolonged by removal and remounting for use of the tape slot on the reverse face of the guide. Nevertheless, after the second slot has been used, the entire tape guide must be discarded and replaced.
Another tape guide with an alternative slot arrangement is shown in U.S. Pat. No. 4,798,267 and has similar shortcomings. The use of non-abrasive material for reducing friction within a tape guide is disclosed in U.S. Pat. No. 5,925,859. The tape guide arrangement of U.S. Pat. No. 5,360,085 is intended to reduce operating noise, and the tape guide shown in U.S. Pat. No. 4,674,603 is directed to facilitating removal and repair. The aforementioned tape guides do not achieve the maintenance expediency and cost economy of the present invention.
Briefly, the nature of this invention concerns an elevator tape guide with redundant guide slots. The tape guide includes a mounting plate adapted for attachment to an elevator cab assembly. The mounting plate accommodates a removable plug member. The plug member includes two tape guide slots with each of said slots being severally registrable with an edge of the tape as needed for wear-replacement. The plug member may be removed and replaced at the end of the useful slot life without discarding the mounting plate.
Having thus summarized the invention, it will be seen that it is a preferred object thereof to provide an elevator tape guide of the general character described herein which is not subject to the previously mentioned limitations.
A preferred object of this invention is to provide an elevator tape guide with a replaceable slot plug member for more effective serviceability and improved maintenance management.
A further preferred object to this invention is to provide an elevator tape guide having a plug member with plural tape slots for expeditious tape slot substitution.
A still further preferred object of the present invention is to provide an elevator tape guide that is practical in use, reliable in operation, relatively simple in design, and economical to manufacture.
With these ends in view, the invention finds embodiment in certain combinations of elements and arrangements of parts by which the aforementioned preferred objects and certain other objects are hereinafter attained, all as more fully described with reference to the accompanying drawings and the scope of which is more particularly indicated in the appended claims.